What is Cilium used for?

Cilium is an eBPF-based networking, security and observability layer for cloud native and Kubernetes environments, covering container networking, policies and load balancing. It is a good fit for Kubernetes cluster networking, enforcing network policy between services and observing traffic in container platforms.

Is Cilium open source?

Yes. Cilium is open source under the Apache-2.0 licence. Its source code is on GitHub at cilium/cilium and is written mainly in Go.

Yes. Cilium is open source, so the software itself is free to use.

Can I self-host Cilium?

Yes. Cilium can be self-hosted on your own server or infrastructure; there is no official hosted version.

What is Cilium an alternative to?

Cilium is an open-source alternative to Illumio.

Is Cilium actively maintained?

Yes. The most recent commit to Cilium was on 2 October 2026, and the latest release is v1.20.2, published on 16 September 2026. The project has 26k stars on GitHub.

Cilium: open-source alternative to Illumio

About Cilium

Cilium is a cloud native project that uses eBPF, a technology that runs sandboxed programs inside the Linux kernel, to provide networking, security and observability for containerized workloads. It is most often deployed in Kubernetes clusters as the container network interface, replacing traditional iptables-based approaches.

Its topics show the breadth of the project: Kubernetes networking and CNI, load balancing, XDP, security, kernel-level monitoring and troubleshooting. Because policies and visibility are implemented in the kernel, it can enforce network rules and observe traffic between services with relatively low overhead. The project website describes it simply as cloud native, eBPF-based networking, observability and security.

Cilium is written in Go and Apache-2.0 licensed, and it runs on your own clusters rather than as a hosted service, though several cloud providers integrate it into managed Kubernetes. It suits platform and security teams that operate Kubernetes at scale and need fine-grained network policy plus insight into service-to-service traffic.

Key features

eBPF-powered Kubernetes networking
Network security policies
Kernel-level load balancing
Traffic observability and troubleshooting
XDP acceleration support
Container network interface plugin

Good fit for

→Kubernetes cluster networking
→Enforcing network policy between services
→Observing traffic in container platforms

Built with: Go; Kubernetes
Tags: ebpf; kubernetes; networking; cni; security; observability; service-mesh; go; cloud-native

Cilium: questions and answers

What is Cilium used for?: Cilium is an eBPF-based networking, security and observability layer for cloud native and Kubernetes environments, covering container networking, policies and load balancing. It is a good fit for Kubernetes cluster networking, enforcing network policy between services and observing traffic in container platforms.
Is Cilium open source?: Yes. Cilium is open source under the Apache-2.0 licence. Its source code is on GitHub at cilium/cilium and is written mainly in Go.
Is Cilium free?: Yes. Cilium is open source, so the software itself is free to use.
Can I self-host Cilium?: Yes. Cilium can be self-hosted on your own server or infrastructure; there is no official hosted version.
What is Cilium an alternative to?: Cilium is an open-source alternative to Illumio.
Is Cilium actively maintained?: Yes. The most recent commit to Cilium was on 2 October 2026, and the latest release is v1.20.2, published on 16 September 2026. The project has 26k stars on GitHub.